Spencer Lewis, the headteacher of Yavneh College in Borehamwood, has joined colleagues from local schools in an appeal to parents to discuss the dangers of drug use with their children.

In a joint letter, the heads said they were “very worried about the rise in the use of drugs by young people”.

They warned that there had been an “alarming growth” in the use of such drugs as ketamine and cocaine.

Social media was making it easier for young people to obtain supplies.

“Signing up to an Instagram feed or linking on Snapchat or WhatsApp or numerous other platforms would enable anyone interested to receive constant updates several times a day on what is available locally and pricing,” they said. “From that point, purchase and delivery is one or two clicks.”

All of their schools had a “zero tolerance” approach to drugs, they said.

“We need to work together to educate the young people to resist and not become caught up in this insidious problem.

“Given the police advice and guidance about what would appear to be an increasingly worrying national picture, we feel it would be useful if all parents were to sit down with their children and discuss these issues relating to drugs.”

Mr Lewis told the JC that  w hilie Yavneh had not noticed increased drug use among its own pupils, it was "concerned about what is a societal problem and challenge for all young people. Parents need to have the correct information, hence our letter."